Brief Answer:
Several possible causes.

Detailed Answer:
I read your question carefully and I understand your concern.

The answer to your question is not that straight forward as there can be many causes for falls.
Orthostatic hypotension is one such possibility, I suppose that's what the first doctor you saw meant. It means a drop of blood pressure when one changes body position from supine to standing. Usually that is verified by measuring blood pressure supine, seated and standing. If there is a significant drop then it is the most likely cause. If in doubt tests like tilt table test can make the diagnosis.

Peripheral neuropathy is another possibility which is commonly associated with balance issues. It can be diagnosed through nerve conduction studies. If diagnosed tests to search for the cause are necessary.

Brain lesions such as stroke are another common cause of falls when in the area of the brain dealing with balance. Other neurological conditions like Parkinson's disease are another common cause as they it may lead to the above mentioned orthostatic hypotension.

Among other causes may be inner ear related disorders as it is also very much involved in balance. If you are under other medications for other purposes their side effects should be considered as well.

So as you may understand to make the distinction between these different causes a thorough physical exam including blood pressure measurements in different positions and a neurological exam is necessary. Afterwards several blood tests, nerve conduction study tests and imaging may be required depending on the findings. Management depends on the established cause.

I remain at your disposal for other questions.

---